Phase 1: Link enrichment + OG preview cards

- Fetch OG/Twitter card metadata for URLs in stories (title, description, image, site)
- Disk cache (.og-cache.json) avoids repeat requests
- 61 links enriched, 50 stories now have OG images
- Link cards with image thumbnail, site name, title, description
- Responsive: side-by-side on desktop, stacked on mobile

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: peas